Conventionally, it is known to provide an undercover which covers the bottom face of a vehicle body. The undercover is provided so as to protect an engine room, etc., from, for example, muddy water and stones splashed by tires and to improve aerodynamic characteristics by covering the unevenness of the bottom face of the vehicle.
With regard to this kind of undercover, for example, Patent Literature 1 discloses an inspection cover 2 that is provided in such a manner as to be slidably retained in an undercover 1 that covers the bottom face of an engine as shown in FIG. 21. Moreover, Patent Literature 2 proposes to provide deformation preventing means that retains the reinforcement beams in the retainer recess of the cover body to ensure the rigidity and strength of the plastic undercover, thereby preventing the beams from being plastically deformed.